1. Technical Field
Example embodiments of the present invention relate to an etching composition, a method of forming a metal pattern and a method of manufacturing a display substrate. More particularly, example embodiments of the present invention relate to an etching composition for etching a metal layer including copper, a method of forming a metal pattern and a method of manufacturing a display substrate.
2. Description of the Related Art
As the size of a display device and the requirements of a customer for a high resolution are increased, the length of the gate line or the data line is increased and the width of the gate line or the data line is decreased so that the electrical resistance is increased. This increase in electrical resistance causes a resistance-capacitance (“RC”) signal delay. The gate line or the data line can be formed from a metal having a relatively low resistance to reduce the RC signal delay.
Copper as a metal having a relatively low resistance and used for forming the gate line or the data line has excellent electric conductivity and is a plentiful natural resource. In addition, copper has a resistance much lower than aluminum or chromium. In contrast, a resistance of copper against an oxidizer is higher than that of aluminum or chromium, so that a strong oxidizer may be used for etching a copper layer.
Korean Patent Publication No. 2000-79355 discloses an etching composition for a copper layer, which includes hydrogen peroxide, an inorganic acid and a neutral salt, and Korean Patent Publication No. 2005-00682 discloses an etching composition for a copper layer, which includes hydrogen peroxide, a copper-reaction inhibitor, a hydrogen peroxide stabilizer and a fluoric ion, and Korean Patent Publication No. 2006-64881 discloses an etching composition for a copper layer, which further includes five additives including a fluorine-containing compound, an organic compound further to hydrogen peroxide, Korean Patent Publication No. 2000-32999 discloses an etching composition for a copper layer, which includes iron chloride (III) hexahydrate and hydrofluoric acid.
When the conventional etching compositions are used for etching a copper layer, an etching ratio to a copper layer or a neighboring metal layer may be excessively great, or an obtained pattern may have an inversed taper shape, which has a taper angle more than 90°. Furthermore, hydrogen peroxide decomposes into water and oxygen through disproportionation in the presence of a copper ion and an iron ion so that heat is generated and its composition rapidly changes. Thus, the manufacturing margin and the storing stability of the etching composition may be reduced. However, addition of a hydrogen peroxide stabilizer may result in increased manufacturing costs.
Furthermore, when the conventional etching compositions are used for etching a copper alloy layer, a taper angle of an obtained pattern may be excessively small, for example, lower than 20° since etching ratios to metals included in the copper alloy layer are different from each other. Thus, substantial etching failures may result. Furthermore, when a taper angle of an obtained pattern is excessively small, the width of the line is substantially reduced so that electrical resistance is increased.